Genes ofEscherichia coliO157:H7 That Are Involved in High-Pressure Resistance

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Abstract
SeventeenEscherichia coliO157:H7 strains were treated with ultrahigh pressure at 500 MPa and 23 ± 2°C for 1 min. This treatment inactivated 0.6 to 3.4 log CFU/ml, depending on the strain. The diversity of these strains was confirmed by pulsed-field gel electrophoresis (PFGE) analysis, and there was no apparent association between PFGE banding patterns and pressure resistance. The pressure-resistant strainE. coliO157:H7 EC-88 (0.6-log decrease) and the pressure-sensitive strain ATCC 35150 (3.4-log decrease) were treated with a sublethal pressure (100 MPa for 15 min at 23 ± 2°C) and subjected to DNA microarray analysis using anE. coliK-12 antisense gene chip. High pressure affected the transcription of many genes involved in a variety of intracellular mechanisms of EC-88, including the stress response, the thiol-disulfide redox system, Fe-S cluster assembly, and spontaneous mutation. Twenty-fourE. coliisogenic pairs with mutations in the genes regulated by the pressure treatment were treated with lethal pressures at 400 MPa and 23 ± 2°C for 5 min. The barotolerance of the mutants relative to that of the wild-type strains helped to explain the results obtained by DNA microarray analysis. This study is the first report to demonstrate that the expression of Fe-S cluster assembly proteins and the fumarate nitrate reductase regulator decreases the resistance to pressure, while sigma factor (RpoE), lipoprotein (NlpI), thioredoxin (TrxA), thioredoxin reductase (TrxB), a trehalose synthesis protein (OtsA), and a DNA-binding protein (Dps) promote barotolerance.

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